Q.20..solve it

​Q20. A driver stars a car from a point P at time t = 0 seconds and stops at point Q. The distance x ( in metres ) covered by it in t seconds is given by r = t²  $\left(2 \frac{t}{3}\right)$. Find the time taken by it to reach Q and also find the distance between P and Q. The driver has stopped the car at the point Q on the roadside to take the call on his mobile phone. Has he done right in doing so ?